Add a display density parameter.

This change add a display density parameter to
vm_tools.cicerone.LaunchContainerApplicationRequest.

This is used to enlarge Crostini windows for some older Linux apps that
don't show well on HiDPI displays by user preferences.

BUG=chromium:839242
TEST=New proto buffer field added and it still compiles.

Change-Id: I963f1bf60281b16110e515891e3a44a3fab6505e
Reviewed-on: https://chromium-review.googlesource.com/1226168
Commit-Ready: Tim Zheng <timzheng@chromium.org>
Tested-by: Tim Zheng <timzheng@chromium.org>
Reviewed-by: Jeffrey Kardatzke <jkardatzke@google.com>
Reviewed-by: David Reveman <reveman@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
diff --git a/dbus/vm_cicerone/cicerone_service.proto b/dbus/vm_cicerone/cicerone_service.proto
index 4f1edcc..bb0f622 100644
--- a/dbus/vm_cicerone/cicerone_service.proto
+++ b/dbus/vm_cicerone/cicerone_service.proto
@@ -118,6 +118,15 @@
 // Request to launch on application in the specified VM/container. Used with the
 // LaunchContainerApplication D-Bus message into vm_concierge.
 message LaunchContainerApplicationRequest {
+  // Display scaling of the app windows.
+  enum DisplayScaling {
+    // Default scaling.
+    UNSCALED = 0;
+    // Windows scaled. Used to scale up older app windows that don't show well
+    // with HiDPI display otherwise.
+    SCALED = 1;
+  }
+
   // Name of the VM to target.
   string vm_name = 1;
 
@@ -135,6 +144,9 @@
   // Files to pass as arguments when launching the application, if any, given
   // as absolute paths within the container's filesystem.
   repeated string files = 5;
+
+  // Display scaling requested.
+  DisplayScaling display_scaling = 6;
 }
 
 // Response sent back by vm_concierge when it receives a